Problem in understanding conventions for delta_cdm values from get.perturbation()

[priy35]

Dear CLASS team,

I am trying to extract the initial conditions for δ_cdm and θ_cdm at a given redshift using the get.perturbation function. However, I am noticing that the values of δ_cdm are consistently negative, even though I am working in the Newtonian gauge.

As per the documentation, the CLASS format should provide the raw δ values, while the CAMB format outputs −δ/k². Since I have not switched to the CAMB format, I expected the δ_cdm values to be positive. Could you please clarify why δ_cdm appears negative in this case?

I would greatly appreciate any guidance on this.

Thank you for your time and help.

Best
Priyanka

[priy35]

@ThomasTram can you please help me with this. I really appreciate any help you can provide.

Best
Priyanka